Check valves are used in a variety of subterranean applications. In some applications involving perforating and fracturing, a frack plug functions as a check valve in that it is normally opened for flow into the delivery string during running in. Once set the plug typically has a ball landed on a seat that prevents flow out through the plug. The perforating gun is positioned above the plug after the plug is set and fired to hopefully create perforations in the borehole. Pressure is applied from above the plug to seat the ball against a seat in the plug so that the pressure will be directed into the newly formed perforations to initiate fractures. This process is repeated in a bottom up direction until the entire wellbore is fractured. Prior to production the frack plugs are milled out and a production line and packer are run in for production from the fractured or treated zone.
Several issues have come up with check valves in frack plugs. One problem is that the ball rotates on the seat when the milling process is attempted. This relative rotation with respect to the valve seat delays the milling process because the ball winds up having to be eroded with rotation against the seat rather than just being milled through with the milling tool. Another problem with traditional ball checks occurs when the perforating gun fails to fire and must be removed and either redressed or replaced. Typically wells getting a plug and perforate treatment are highly deviated and require the use of flow from the surface to push a wireline supported gun to the desired location. This usually entails packer cups associated with the gun that stop the flow around the gun enough to fluidly power the gun to the desired location. The problem is that when the gun fails to perforate and the traditional check valve in the frack plug will not pass any fluid in a downhole direction, there is no way to use flow to deliver the replacement gun to the desired location.
A solution was earlier proposed by the inventor of the present invention in an application filed Apr. 23, 2015 in the U.S. having a Ser. No. 14/694,350 where the ball for the frack plug is only delivered if the gun fires. This design entailed an acceleration sensitive locking system to drop the ball in response to the acceleration created when the gun was fired. This design addressed the problem of the gun not firing but not the issue of the difficulty in milling out a ball that spins on its ball seat during the milling process.
Spring loaded ball check valves with non-metallic components are shown in hydraulic systems in U.S. Pat. No. 5,454,399. Check valves with a ball captured for two directional free movement are shown in U.S. Pat. No. 5,785,083. Flow responsive valves to prevent blowouts are shown in U.S. Pat. No. 4,628,996. WO98/03766 shows in FIG. 8 a ball supported in a web in the seat opening that is responsive to flow. The support impedes flow due to its placement and is subject to erosion from fluid velocities due to placement in the seat opening.
Some subterranean tools are operated with axial relative component movement. The valve of the present invention can be linked to a movable member to create the relative movement when the valve is in the closed position so that pressure delivered against the check valve in the closed position will create the relative movement in the associated subterranean tool once flow above a predetermined value is reached to close the valve. Upon reduction of pressure applied to the valve after the relative movement, the check valve automatically moves back to an open position to allow flow in the same direction of flow that previously closed the valve.
The present invention addresses the issue of spinning when milling out, having to run in a replacement gun with no perforations, expediting the milling process and providing a way to get limited flow for gun redelivery with cutting off flow with larger flow rates in a simple design where components have multiple functionality to make the overall design simple and more amenable to reliable operation with nonmetallic material for expediting millout. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be found in the appended claims.